In the related art, there are known image acquisition apparatuses that perform distance measurement (for example, see Patent Literature (PTL) 1).
Such an image acquisition apparatus is provided with a microlens array that is located between an image acquisition lens that focuses light from a subject and an imaging device that captures the light focused by the image acquisition lens, at a position between a real image formed by the image acquisition lens and the imaging device.
The light focused by the image acquisition lens is formed into a real image and is then imaged at different positions in an imaging plane of the imaging device by microlenses constituting the microlens array. As a result, parallax images are acquired for the respective microlenses. Then, stereo matching is performed for the acquired parallax images, thus measuring the distance to the subject.